1. Field of the Invention
The present invention relates to an electric bed in nursing beds or the like, which can electrically lift up the back portion of the bed, and, more particularly, to an electric bed capable of lifting the back portion up without shifting a carereceiver, such as a patient, who is lying. or applying pressure on the carereceiver, and a control method and a control apparatus for the electric bed.
2. Description of the Related Art
In an aging society where the number of bedridden patients is increasing, it is necessary to set up the upper body of a patient on a bed for various purposes, such as a medical examination, eating a meal, watching a TV and reading a book. In this respect, electric beds which can electrically lift the back bottom and knee bottom of the bed up and down have been developed. However, back lift-up or back lift-down of an electric bed shifts the body of the patient or applies pressure on the patient. This results in the deviation between shift muscles and skins so that fine blood vessels extending from the muscles to the skins are stretched, thus making it likely to cause blocking of the blood vessels or interruption in the circulation of the blood. This damages the skins. It would put a significant burden on a caregiver or a carer to return the body of a bedridden patient, whose position has been shifted due to a back lift-up operation or back lift-down operation, to the original position because the patient cannot move himself or herself.
Further, at the time a patient on a bed who is not bedridden is moving on a wheelchair from the bed, lifting up the upper body of the patient on the bed makes it easier for the patient to take a sitting position on the bed, thus facilitating shifting of the patient onto the wheelchair. In this case, it is also desirable not to cause deviation on the body or apply pressure on the body at the time of lifting up the upper body of the patient.
There is a back/knee interlocked movement control method which is designed to solve the problems and makes an electric bed that ensures back lifting and knee lifting easier to use by changing the timing of an electrically powered back lift-up operation and knee lift-up operation or preventing the angle between the back bottom and the knee bottom from becoming unnecessarily narrower (as disclosed in Patent Document 1: Japanese Patent Laid-Open No. 2001-37820).
While the prior art described in the publication can independently control the back lift-up operation and knee lift-up operation, however, the back lift-up operation and knee lift-up operation are basically carried out separately. That is, an operator (caregiver) performs operations to start and stop back lifting and start and stop knee lifting. To prevent a patient from slipping by the back lifting, an operation to lift up the back bottom is performed after lifting the knee bottom up by 20 to 30°. While this prior art can achieve the original purpose, such an operation, if done by a carer, is a subjective operation of the carer, so that slipping of the patient's body at the time of lifting up the back of the patient cannot be prevented sufficiently. It is not also possible to surely prevent a patient from having an oppressive feeling in the back lift-up operation and back lift-down operation.